Variable capacity reservoir



June 10, 1941- T. c. ArrcHlsoN 2,245,247

VARIABLE CAPACITY RESERVOIR Filed Nov. 3, 1939 Figi.

FlLLED WITH FILL s L T UQUPD IN U A 10N 3 Inventor-z Thomas C. Atchison,

Patented June 10, 1941 2,245,247 VARIABLE CAPACITY aasnavom Thomas c.Aitchison, Pittsfield, Mass., assignmto General Electric Company, a.corporation of New York Application November 3, 1939, Serial No. 302,746

7 Claims.

'I'he present invention relates to variable capacity reservoirs for usein supplying oil or other insulating liquid to or receiving it fromcable systems and parts thereof as the volumeof the liquid changes withtemperature changes. As examples. such reservoirs may be utilized tosupply liquid insulation to terminals connected to conductors of cablesystems and to the casings enclosing the joints which unite adjacentends of insulated electric conductors. The cables may be of theso-called solid type or of the fluid filled type. The general purpose ofthese reservoirs is to ensure the complete lling of the parts of thecable system, however it is constructed, with sulilcient liquidinsulation to prevent the formation of objectionable voids within thecable sheaths and other parts forming thel enclosure of the insulatedconductors.

'Ihe present invention isin the nature of an improvement over theconstruction set forth in the patent to Eby 1,823,731, issued September15, 1931, and has for its object the provision of a reservoir which isless costly in construction than those heretofore employed to the endthat their wider use may be economically justified. In this connection,it may be pointed out that such reservoirs on account of the care whichmust be exercised in their manufacture are relatively expensate fordifferent elevation of parts of the cable, as in the so-called balancepressure cable systems.

For a consideration of 'what I believe to be novel and my invention,attention is directed to the accompanying description and the claimsappended thereto.

In the accompanying drawing which is illustrative of my invention, Fig.1 is a view in side elevation of a reservoir with certain parts brokenaway to illustrate the interior construction; Fig. 2 is an enlargedview, chiefly in section. of a part of one of the reservoir cells Fig. 3is a view showing the application of a gas lled tank to a reservoir bywhich a greater amount of gas is made available to suit the servicerequirements; and Fig. 4 is a detail sectional view of the breather forthe reservoir.

The tank or casing of the reservoir comprises two truly cylindricalparts 4 and 5 which may be made of thin gauge steel or equivalentmaterial. The purpose in using thin material is to reduce weight andcost. The reservoirs are commonly supported from the roofs of manholesand on that account all reductions in weight which can be made in thetank and contained parts are highly desirable. Manholes are usuallyrelatively small and crowded so that reduction of weight of thereservoirs is one of the many considerations. The halves of the casingare made separately and for a short distance near the center of thetank, considered as a whole, are in telescopic relation as indicated at6. The joint is subsequently brazed or soldered so the tank will bepressure tight. 1 and 8 indicate straps by which the tank can besuspended from the ceiling of the manhole or other containing structure.The halves of the tank are each truly cylindrical as distinguished fromthe tank of the said Eby patent which has a longitudinal enlargement orbulge to receive a manifold, as shown in Fig. 5 thereof. By doing awaywith a manifold, the parts become simpler to construct and also lessexpensive because less metal is employed. The elimination of themanifold does away with the projection or bulge in the wall of the tankwhich accommodates it. This results in a simpler and cheaper tank andalso simplifles the manufacturing operation of uniting and soldering thehalves of the tank at the center. The actual inside diameter of the tankfor the same class of service is or may be the same as that of priortypes but the elimination of the bulge will reduce the overall dimensionby about two inches. The more important feature is, of course, thereduction in the cost of manufacture. The reason why no manifold isrequired will appear later on. r

Within the tank or casing is a relatively large number of similar cells9 made of disks of thin sheet metal, the central portion of each sidewall being corrugated to increase the flexibility. The peripheralflanges or edges I0 of each pair of disks forming a cell are suitablyunited as by electric welding, for example. The cells are placed side byside in the tank to form a group. Where the interior of the cells isopen to the atmosphere, as is the voirs, the metal used in theirmanufacture should be non-corrosive whereas for the other types commonsteel may be used. In respect to the features just above mentioned, thearrangement shown in Fig. 6 of the Eby patent may be followed. However,there is this important diiference. In the patented structure there isno means whatsoever to enable the gas pressure within the cells to beadjusted whereas there is s uch a means in the present structure. Thisis of particular importance in balanced pressure cable systems becausethe pressure in the cells of one reservoir can thus be readily adjustedwith respect to those of another reservoir to take care of differencesin the profile of the cable, by the admission of more or less gas underdetermined pressure. The gas employed may be air but desirably is ofakind such as CO2, for example, that does not inthe case of a leakingcell seriously affect the cable oil or other liquid which before use iscarefully degasied. Thecells of the reservoir are submerged in the oilor other liquid from the cable. Where a manifold is used, the cells areconnected thereto in parallel and, because of the viscosity of theliquid, the manifold and the pipes connecting the cells and manifoldhave to be of substantial cross-sectional area to reduce the resistanceto iiow. Because no manifold is employed with cells connected thereto inparallel, a further departure from the patented structure is made inthat the cells are connected in series relation one to the other.Because the cells are filled with gas which moves freely, asdistinguished from a4 liquid which moves more slowly, the tubesconnecting the cells in series relation may be made of much smallercross section than where liquid is employed. The gas pressure within thecells may be that of atmospheric air for the gravity feed type ofreservoirs, and at an elevated pressure for the pressure type reservoirsand also for the balanced pressure type.

In Fig. 2 is shown on an enlarged scale a portion of one of the cells,which cells are all similar in construction. II and I2 indicate thecorrugated side Walls or disks of a cell, and I3 the portions thereofwhich extend toward each other, the high parts of the corrugations aswell as the low parts being respectively in vaxial register so as to beself supporting under certain pressure conditions. Each of the sidewalls is provided with a attened inset or depressed portion I4 which hasan opening to receive a thimble or ferrule I5, the latter having a borein which an end of the connecting tube or conduit I6 is snugly fitted,after which the parts are united and sealed as, for example, bysoldering, brazing or welding. The thimbles are seated and sealed in thewalls of the cells prior to the operation of uniting the flanges of thewalls. The thimbles desirably have enlarged heads so as to ensure a goodjoint between them and the thin walls. The headsv are desirably locatedinside of the cell to facilitate the assembly operation, but may belocated outside if desired. The flattened or inset portions Il of thetwo side walls are angularly displaced to permit of the use ofreasonably long and relatively flexible tubes or conduits I6 so as toprevent injury thereto caused by vibration, improper handling of thegroup of cells, etc. The tubes are desirably bent to conform generallyto an annular portion of each cell. By connecting the ends of the tubes,one to one cell wall and the other to the wall of an adjacent cell, al1of the cells of a group are connected in series relation. It will benoted that the peripheral portions or flanges of the side walls extendradially welll beyond the tubes I6 and thus protect them from injury,particularly during manufacture. Due to this ararngement, the cells whenassembled into a group can behandled as a unit without injury -to thetubes.

It will be noted that each tube I6 is connected at one end to theleft-hand side wall of one cell and at the opposite .end to theright-hand wall of the adjacent cell. This has the advantage that thetubes do not have to cross over the flanges I0 where they would beliable to injury, and also the tubes may be made shorter for the sameangular spacing of the insets I4. Due to the protection afforded by theflanges I0 which have a substantially greater diameter than that of theregion of the side Walls containing the insets, the tubes may be oflight section and hence more easily bent to the desired shape. The useof thimbles facilitates the making of the connections between cells, asWill be seen from inl spection.

Where it is desired to have the cells operate at atmospheric pressure,as in a gravity feed reservoir, the outermost cell is connected by meansof a relatively long tube or conduit I1 to a breather I9 which maintainsthe chambers of the cells at atmospheric pressure. The breather I9 isdesigned so as to prevent foreign matter or free water from entering thechambers of the cells. Atmospheric air flows into and out of thebreather' through holes ISE, Fig. 4, in the base and then up through amass of glass wool IIIh or other equivalent material and then downthrough the central tube I9c into the cells. Thus foreign matter or freewater entering through the holes in the base is trapped in the massofglass wool and prevented from entering the central tube leading to thecells. With the chambers of the A cells directly exposed to-the effectsof atmospheric air, the walls thereof will move toward and away fromeach other to a limited extent with changes in temperature; thus suchchanges will be automatically compensated for. Because the walls aredirectly exposed to atmospheric air, they will respond to changesthereof more quickly than would be the case if the action was indirectas through -a body of liquid.

Where it is desired to have the cells operate on a balanced pressuresystem, an outermost cell is connected by means of a relatively longtube or conduit 3I, Fig. 3, to an automatically closing gas valve 4I,such as may be used for automobile inner tubes or other purposes. Bychanging the pressure of the gas within the group of cells, as byadmitting gas at the desired pressure or by opening the valve andpermitting gas to escape, the force exerted by the walls of the cell onthe liquid in th'e tank may be changed or adjusted at will.

The cells are secured in a holder which4 comprises a pair of heads 2|,Fig. 1, of which one is Y shown, the heads being held in adjustedposition by a suitable number of angularly spaced clamps or members 22,the ends of which vare turned.

- cable, terminal or other device connected thereto.

The tting is also provided with aA shut-o valve and a filling port 28through which oil may be added to the reservoir and the pressure thereofmeasured by means of a gauge. 'Ihe opening in the iitting through whichtheliquid flows to and from the cable is of substantial size so that theresistance to i'low is small, smaller in fact than the resistance .toflow due to the use of a manifold and the tubes connecting the cells inparallel thereto as has been the Practice heretofore.

In Fig. 3 is illustrated an arrangement which is more especiallyintended for a balance pressure reservoir in which it is desirable tohave a greater gas space. This is provided for by having an auxiliarychambered tank 29, one end of which is telescoped over one end of themain tank containing the cells in the same manner as the two halves ofthe main tank are arranged, and in like manner the tanks are soldered orotherwise united in a gas-tight manner. It is necessary where anauxiliary tank is used to connect it with the cells in the main tank.The conneciion may be external to the tanks or internal. The externalarrangement will first be described. The left-hand head of the main tankhas a boss 30 secured thereto, and a tube Il permits introduction orwithdrawal of gas from the cells. Its function is similar to tube l1 ofFig. 1, the difference being that the gas passing therethrough is underpositive pressure. The periphery of the boss is screw-threaded, andseated thereon is a tubular member 32 having an internal screw thread.The member has a central bore, and opening into it is a lateral passagethe outer end of which is screw-threaded to receive the elbow 33. To theauxiliary tank 25 is secured an elbow 34, and the two elbows areconnected by a tube 35, the connection between the tube ends and theelbows being accomplished by detachable compression ttings 36. Theexposed head of the main tank is also provided with a tting l2 havingthe functions of parts 21 and 28 of Fig. 1.

The internal arrangement will now be described. 'Ihe right-hand head ofthe main tank is provided with a boss 25 which is welded or otherwisesecured thereto. Extending through the boss and sealed therein is a tube25, one end of which opens into the chamber of the auxiliary tank 28 andthe other end into the chamber of a cell, the connection between thetube and the cell being similar to that shown in Fig. 2. Thisconstruction has the advantage that all of the tubes are within thetanks and hence are fully protected by the walls thereof from injury.'I'he external arrangement, on the other hand, has the advantage thatthe parts are accessible from the outside of :the tank. For mostinstallations the internal arrangement is the more desirable. Shouldoccasion arise, both internal and external arrangements may be employed.

Due to thel auxiliary tank, a large volume of gas under determinedpressure is constantly available for supplying fthe cells of the mainreservoir with gas, the cells as before compressing when the liquidpressure of the main reservoir or tank rises and expanding when thepressure `drops. This arrangement thus ensures a proper pressure on theliquid in the cable, terminal or other device to which the reservoir isconnected. and is particularly useful in obtaining full displacement ofthe walls of the cells at the lowest cable pressure. 'Ihe member 32 hasa shoulder and a part of reduced cross section, the said part beingexternally screw-threaded to receive a sealing cap I1. Between the capand shoulder is a packing 3l to seal the joint. 'Ihe member has ascrew-threaded .plug 39 through which gas under pressure may be admittedto or removed from .the cells through the tube 3|. The plug has asuitable valve 4| such as may be used on automobile inner tubes whichopens 'to admit gas under pressure superior to that in the cells andautomatically closes when the connected supply pipe is removed from theouter end of the valve. Oil or other liquid is admitted to the tankthrough a fitting 42 which is similar to parts 21 and 28 of Fig. 1.

For the purposes of illustration, the fittings in Fig. 3 have beengreatly enlarged with respect to the tank so that the interior parts maybe shown. In practice, they bear substantially the relation to the tanksas shown in Fig. l,

From what has been said it will be noted that when the reservoir is usedas a gravity feed device the tank will be completely filled with oil ascontrasted to a filling composed of atmospheric air and a limited amountof immersion oil as in the prior design as exemplified by the Ebystructure. This arrangement. decreases the opportunity for rust to form.It also results in a reduction of cost since all the parts except thecells may be made of common steel instead of non-corrosive material.'I'he fact that the tank is lled with oil means that the inside wallthere l on first consideration appear relatively simple, is

nevertheless of m-aterial importance. One of the major dimculties withthe old type of reservoir is the amount of time required to locateminute gas leaks which sometimes occur in service. There have been caseswhere several weeks have been spent by the operators of public utilitiesin trying to locate minute gas leaks in the old type reservoirs withoutsuccess and nally the reservoirs had to be removed from the connectedcable and manhole before repairs could be made.

In this connection it should be borne in mind that repairs on hightension cable systems can be made with safety only when the cable is outof service. Obviously a utility is not in a position to shut down atwill important cables in its system on account of interruption ofservice to customers. Furthermore, because the oil used in the cable ishighly degasifled, the job of removing ,one reservoir and substitutinganother is not as simple as it would first appear. It requires care toprevent the entrance of foreign matter into :the cable and evacuation ofthe' connecting pipes and other parts, and may even require a vacuumtreatment of the cable ends terminating in the joint casing where thereservoir connections are made. All operations involving the opening ofa cable have to be performed with the utmost care. With my improvedconstruction, where the tank is completely filled with oil underdetermined pressure, minute leaks, should they appear, are relativelyeasy to locate because the oil smudges the outside of the tank at theplace of leakage which would not be :the caseA if the tank were lledwith gas. v

What I claim as new and desired to secure by Letters Patent of theUnited States, is:

1. A variable capacity reservoir comprising a sealed tank adapted tocontain a body of liquid, conduit means through which the liquid flowsbetween the tank and the apparatus served thereby, a pluralityofdndividual sealed chambered cells having side walls movable toward andaway from each other as the volume of the liquid changes, the cellsbeing located within the tank and submerged in its contained liquid, incombination with conduits connecting the cells one to another in seriesrelation, and a conduit for admitting gas under determined pressure toone of the cells and through it to the others, one end of the conduitbeing accessible from outside of the tank.

2. A variable capacity reservoir comprising a main sealed tankcontaining a body of liquid, conduit means through which the liquidflows between the tank and the apparatus served thereby, a plurality ofchambered cells submerged in the body of liquid, in combination withconduit means connecting the chambers of .the cells in cell chamberswith the interior of the auxiliary tank and through which gas issupplied to the other cells. 4

3. A variable capacity reservoir comprising a tank adapted .to containliquid, a group of chambered cells submerged therein, each cell havingflexible disk-shaped side walls united at -their peripheral edges, eachwall having an inset portion, conduits entering the walls of the cellsthrough the insets, each conduit ex'tending from the inset of one cellwall to a similar inset in the wall of the cell immediately adjacentthereto to connect them in series relation, and means for admitting uidto one of the cells under a determined pressure.

4. A variable capacity reservoir comprising a tank containing liquid, agroup of chambered cells submerged therein, each cell having a pair ofright and left-hand disk-shaped side walls, the peripheral edges of thedisks being united to form chambers, each side wall having an insettherein, a thimble mounted in each of the insets, a tube connecting thethimble of a righthand disk with the thimble of a left-hand diskto-connect the chambers of the cells in series relation, and means foradmitting elastic fluid under determined pressure to one of the chambersfor supplying the others.

5. A variable capacity reservoir comprising a tank containing a body ofliquid, a group of cells submerged in the body, 'each cell having a pairof disk-shaped flexible side Walls which between them define a chamberand hlave peripheral flanges, each side wall having an opening, theopenings in each cell being in angularly spaced relation to increase thedistance between the opening in adjacent Walls, a tube located betweenthe anges of each pair of adjacent cells for conveyingfluid from anopening in one cell to an angularly displaced opening in an immediatelyadjacent cell, and means for admitting fluid under determined pressureto one of the group of cells, the tubes connecting the chambers of thecells in series so that all are subjected to the effects of the iiuid.

6. A variable capacity lreservoir comprising a tank, a plurality ofexpansible and contractible chambered cells located therein, individualconduits arranged to connect the chambers of the cells in seriesrelation, a filling of gas for the chambers and conduits, tubular meansconnected to one of the .cells through which fluid may be introducedinto the chambers of all of the cells or Withdrawn therefrom, and aiilling'of liquid for the tank which completely surrounds the chamberedcells.

7. A variable capacity reservoir comprising a tank containing liquid, agroup of gas filled chambered cells arranged side by side and submergedin the liquid, each cell comprising a pair of flexihlfe disk-shaped sidewalls having anges of larger diameter than .the walls for uniting them,conduits opening into the chambers of the cells for connecting them inseries relation, the conduits being located in the spaces-betweenadjacent pairs of anges and protected thereby, each conduit beingconnected at one end to a side wall of one cell and ait the other end tothe adjacent side Wall of another cell, the points of connection to thewalls being angularly displaced, and conduit means admitting gas to oneof the cell chambers.

l THOMAS C. AITCHISON.

